import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int[] a = new int[n];
        int[] count = new int[100];
        for(int a_i=0; a_i < n; a_i++){
            a[a_i] = in.nextInt();
            count[a[a_i]]++;
        }
        int sum = 0;
        for(int b_i=0; b_i < 99; b_i++){
            if(count[b_i]+count[b_i+1] > sum)
                sum = count[b_i]+count[b_i+1];
        }
        System.out.println(sum);
    }
}